A transmission device for a hybrid motor vehicle, comprising two clutches and an electric machine disposed between the internal combustion engine of the vehicle and its gearbox, is known. Such a device is described, for example, in the document FR 2 830 589. Each of the clutches has a friction disc, a release bearing, and a pressure plate mounted axially movably with respect to said reaction plate between an engaged position in which the friction disc is clamped between said pressure and reaction plates, and a disengaged position. The two clutches are disposed on either side of the electric machine. The pressure plate of a first clutch, disposed on the engine side, is configured to be associated with the crankshaft of the internal combustion engine. The friction disc of the first clutch is mounted rotationally integrally with an intermediate shaft that is fastened to a support hub of the rotor of the electric machine. The pressure plate and the reaction plate of the second clutch, which is disposed on the gearbox side, are mounted rotationally integrally with said support hub of the rotor, and the friction disc of said second clutch is intended to interact with an input shaft of a gearbox.
The clutch on the engine side thus allows the crankshaft of the internal combustion engine to be rotationally coupled to the rotor of the electric machine, and the clutch on the gearbox side allows the rotor to be coupled to the input shaft of the gearbox. The internal combustion engine can thus be shut off at each stop, and restarted thanks to the electric machine. The electric machine can also constitute an electric brake, or can provide additional energy to the combustion engine to assist it or prevent it from stalling. When the engine is running, the electric machine can act as an alternator.
The electric machine can be a reversible rotating electric machine of the alternator/starter type or of the motor/generator type. In a starter-type operating mode the clutch situated on the engine side is engaged, and the electric machine allows the internal combustion engine to be started. In an alternator-type operating mode the electric machine allows a battery to be charged, and/or allows energy-consuming components or accessories to be powered when the internal combustion engine is running. It is furthermore configured to recover energy upon braking of the vehicle. The electric machine can be configured in particular to stop the internal combustion engine, for example, at a red light or in traffic jams, and then to restart it (“stop and go” function). In an embodiment, it is capable of furnishing additional power that makes it possible to prevent the engine from stalling (“boost” function). The electric machine can furthermore be capable of driving the vehicle at least for a short distance, the clutch situated on the engine side then being disengaged and the internal combustion engine shut off.
A device of this kind is relatively complex, costly, and bulky.
Patent Application DE 10 2015 211 436 discloses a transmission device for a hybrid vehicle, having in particular:                a torque input flywheel rotationally integral with a crankshaft of an internal combustion engine;        a torque output hub rotationally integral with an input shaft of a gearbox;        a support rotationally integral with a rotor of an electric machine;        control means capable of rotationally coupling the flywheel and the rotor via a first torque transfer path having elastic damping means and having no clutch means, said control means being capable of rotationally coupling the flywheel, the rotor, and the input shaft of the gearbox via a second torque transfer path having said elastic damping means and clutch means.        
In the first operating mode the electric machine, and more particularly the rotor, can therefore rotationally drive the crankshaft so as to restart the electric motor if it has been stopped (“stop and go” function). Furthermore, in the second operating mode, if the clutch means are in an engaged position, the input shaft of the gearbox can be rotationally driven by the combustion engine.
In the first operating mode, the coupling between the flywheel and the rotor is implemented with the aid of toothed members. In the context of a rotational coupling of this kind, it is important to limit the torque transmitted from the rotor to the flywheel, given the risk of generating jolts and of prematurely degrading said toothed members and/or the combustion engine. Achieving torque control of this kind in a practical context is complex.